The present invention is generally in the field of biological control of insect pests, specifically in the area of use of entomopathogenic fungi for the control of cockroaches.
Blattella germanica (the German cockroach) and Periplaneta americana (the American cockroach) are ubiquitous throughout the world. They are the major insect pests in residences, restaurants, hospitals, dormitories and warehouses. Cockroaches are unsightly and have been implicated as vectors of several human disease agents.
The most common means of roach control is the regular spraying of chemical insecticides. Not only are these insecticides expensive, but their long term effects on the inhabitants of the places in which they are used, as well as the environment, are unknown in most cases and potentially hazardous. Further, there is a tendency among the treated insects for resistant strains to develop, which requires the use of large quantities and different chemicals to treat.
Insect pathogens are a possible alternative to the common use of highly toxic chemical insecticides for the control of insect pests. Fungi are one of the promising groups of insect pathogens suitable for use as biological agents for the control of insects.
Fungi are found either as single cell organisms or as multicellular colonies. While fungi are eukaryotic and therefore more highly differentiated than bacteria, they are less differentiated than higher plants. Fungi are incapable of utilizing light as an energy source and therefore restricted to a saprophytic or parasitic existence.
The most common mode of growth and reproduction for fungi is vegetative or asexual reproduction which involves sporulation followed by germination of the spores. Asexual spores, or conidia, form at the tips and along the sides of hyphae, the branching filamentous structures of multicellular colonies. In the proper environment, the conidia germinate, become enlarged and produce germ tubes. The germ tubes develop, in time, into hyphae which in turn form colonies.
The fungus Metarhizium anisopliae is an example of a fungus that infects certain species of insects. This fungus has been administered to insect pests by a number of methods, including direct spraying, injection, and by the application of the fungus to the plant material on which the insect lives or feeds. In some insect species, infection with the fungus has been shown to result in death. In one species, infected individuals were able to transmit the fungus to non-infected members of their colony.
To date, the majority of work evaluating entomopathogenic fungi for biological control of insect pests has focused on applications involving agriculturally important insect pests and mosquitoes. Metarhizium anisopliae is one of the most widely studied fungus for biological control of insects. However, there are few reports which address the ability of M.anisopliae to infect cockroaches. Gunnarsson, S.G.S., J. Invertebr. Pathol. (46)3, 312-319, (1985), for example, has shown that Periplaneta americana exhibits a defense reaction (nodule formation) to the injection of M. anisopliae conidia. However, no mention of the potential of the fungus for roach control was made. In fact, it can be implied from the data that the American cockroach has a strong defense to injected M. anisopliae spores. Further, there are a number of insect species which are not infected by contact with entomopathogenic fungi.
No one has yet developed a consistent and commercially viable way of infecting insects and assuring that the fungi are dispersed throughout the breeding populations. For example, with reference to cockroaches, it is clearly impractical to use a method such as the one referenced above requiring inoculation of individual insects with the fungi.
As of this time, there has been no successful demonstration by others of the practical, reliable and economical employment of an entomopathogenic fungus for the management and biological control of insects infesting houses or buildings.
It is therefore an object of the present invention to biologically control cockroaches using entomopathogenic fungi.
It is a further object of the present invention to provide a device for the convenient, reliable and economically feasible application of fungi in the biological control of cockroaches.
It is a further object of the present invention to provide a method and means for infecting all cockroaches in a breeding colony by dissemination of fungi pathogenic for cockroaches.
It is another object of the present invention to provide a method and means for infection and killing of cockroaches by a variety of fungi so that development of resistant strains is avoided.